class_docstr: Begin(state_name) is a Plex action which causes the Scanner to
  enter the state |state_name|. See the docstring of Plex.Lexicon
  for more information.
code: def __init__(self, state_name):
      self.state_name = state_name
  
label_desc: Use image node_id 1 to create a new Begin object from inherited base classes: Action with example: obj = Begin(state_name)